1. Field of the Invention
The present invention relates to a semiconductor laser of a surface-emitting type in which a light is emitted therefrom in a direction perpendicular to a surface of a crystalline substrate.
2. Description of the Prior Art
As an example of the conventional semiconductor laser of a surface emitting type, there has been described a laser in "Microcavity GaAlAs/GaAs Surface-Emitting Laser with Ith=6 mA", K. IGA et al, Electronics Letters, 29th Jan., 1987, Vol. 23, NO. 3, pp. 134-136. FIG. 4 shows constituent portions of the semiconductor laser described in this article, the portions being related to the present invention.
In this structure, the laser comprises an n-side ohmic metal (AuGe) 21, an n-GaAs substrate 22, a reflective multilayer of SiO.sub.2 /TiO.sub.2 23, an n-AlGaAs clad layer 24, an active layer of GaAs 25, a p-AlGaAs clad layer 26, a buried layer 27 formed by the second growth, an insulation layer 28, and a p-type ohmic electrode (AuZn) 29 also functioning as a reflection mirror.
The conventional semiconductor laser of a surface-emitting type has been attended with the following problems.
(1) There are required two crystal growth processes.
(2) Since the light is emitted from a rear surface of the substrate, this structure is not suitable for an optoelectronics integrated circuit (OEIC).
(3) A film or layer 23 having a high reflection factor is required to be fabricated on a light emitting side.
(4) A region of AuZn is employed as an electrode 29 on the side of grown layers (on the side from which the light is not emitted) and is also used as a reflection mirror. In order to prevent the electrode 29 from forming an alloy with the clad layer 26, which lowers the reflection factor, there is first disposed an insulation film 28 so as to fabricate therein a ring-shaped window to establish a contact between the clad layer 26 and the electrode 29; in consequence, the manufacturing processes become to be complicated and there cannot be developed a favorable ohmic contact, which leads to a high resistance.